The present invention relates to a process for producing a 1,2-naphthoquinone-2-diazide derivative, such as 1,2-naphthoquinone-2-diazide, a salt of 1,2-naphthoquinone-2-diazide-5-sulfonic acid, or that of 1,2-naphthoquinone-2-diazide-6-sulfonic acid, which is important as a starting material for preparing an azo dye, a photosensitive component of radiation-sensitive positive-type photoresist compositions, a positive-type photosensitive lithographic printing plate, etc.